Reproduction, migration, and prospects for persistence of a reintroduced population of an imperiled riverine fish, Robust Redhorse (Moxostoma robustum)

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Abstract

Human modification of the world’s landscapes and riverscapes have resulted in a high number of imperiled species worldwide. Nearly half of North American catostomid fishes are considered imperiled. The conservation of any imperiled species relies on understanding threats and requirements of the species at each life history stage. This study focused on assessing the reproductive biology of an imperiled large-bodied catostomid native to the southeastern United States, the Robust Redhorse (Moxostoma robustum). Robust Redhorse conservation has been hampered by failure to document recruitment. Therefore, gaining knowledge of the species’ reproductive biology could provide managers with information critical for conservation. This study has documented (a) a new method using passive acoustic monitoring to assess spawning frequency of large-bodied catostomids when visual observations can not be made, (b) spawning frequencies and diel periodicity of Robust Redhorse in two river systems, (c) reproductive and migratory behavior of Robust Redhorse in a reintroduced population, compared to two wild, Coastal Plain populations in Georgia, and (d) evidence of recruitment in a reintroduced population of Robust Redhorse. These studies provide novel findings of Robust Redhorse behavior. I have documented Robust Redhorse use of reservoirs as wintering habitat as well as plasticity in use of river and reservoir as wintering habitat. I have also documented plasticity in use of spawning sites, tracking movements by three individuals between two spawning sites during a single spawning season. This study is the first to document nocturnal spawning; Robust Redhorse spawn at all hours of the day with a peak number of spawns after midnight and in the early hours of the morning. Robust Redhorse also display a range of numbers of individuals participating in spawning acts, in addition to the typical trio of two males and a female. I have also documented an alternate reproductive tactic of sneaking spawn attempts, rather than holding territories, by smaller, presumably younger Robust Redhorse males. These new findings and others in this study expand our understanding of reproductive behavior of this imperiled fish species and should provide valuable information for management of this species and future reintroductions.